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...﻿Evolution of Atomictheory
In 1803 John Dalton first proposed the idea that everything is made of tiny solid objects. He wondered how water and air could occupy the same space at the same time, when obviously solid bodies can't. If the water and air were composed of discrete particles, Dalton reasoned, evaporation might be viewed as a mixing of water particles with air particles. He performed a series of experiments on mixtures of gases to determine what effect properties of the individual gases had on the properties of the mixture as a whole. From this he concluded that atoms are indivisible and indestructible. All atoms of a given element are identical in mass and properties Compounds are formed by a combination of two or more different kinds of atoms. A chemical reaction is a rearrangement of atoms. These ideas have come to be known as the "billiard ball” model John Dalton used evidence from his experiments with gases to show that there are many types of atoms, not just one kind. He came up with the concept of elements and compounds. He thought incorrectly that gas elements such as oxygen come as single atoms which can't be broken. His atomictheory has since been superseded.
Then in 1897 JJ Thompson built on the work of these tiny solid balls making up matter and asked how they worked and held together and wondered if they were more complex, so Thomson started experimenting with currents of...

... These atoms CANNOT be further split into smaller portions.
2. At this point, the atomists entered into what their predecessors had postulated to be the origin of matter, namely water (Thales), air (Anaximenses), fire (Heraclitus) and earth (Empedocles). They said, quite accurately as we know today, that these four elements are not primordial substances, but are composed of atoms like everything else.
3.
– All matter consists of tiny particles called atoms
- Atoms are indestructible
- All atoms of an element are identical
- Atoms of different elements have different masses
- When elements react, their atoms combine in simple, whole number ratios
Some of the details off Dalton’s original theory are now known to be incorrect. But the core concepts of the theory (that chemical reactions can be explained by the union and separation of atoms, and that these atoms have characteristic properties) are foundations of modern physical science.
4. Dalton and a few Greek philosophers proposed that matter is discrete. Beyond a certain point, a substance cannot be cut into smaller pieces that retain the properties of the whole. They called the smallest possible piece an “atom”.
5. Sir William Crookes gained more knowledge about the mysterious green glow when he created a bent Geissler tube in 1875. He noticed that the glow was the most intense opposite the negative electrode, also called the cathode. Crookes reasoned that rays traveled...

...Dalton, Thomson to Rutherford,
Bohr and Schrödinger
The Atomic Timeline
Aristotle – everything is made of 4 elements: earth, air, fire water (~360 BC)
This belief is held firm among scholars
until the 17th century.
Sir Isaac Newton is among the first
academic heavyweights to subscribe
to the atom theory.
The Atomic Timeline
John Dalton – offers the first real evidence and science for the
existence of atoms (1803)
He laid down 5 key postulates:
1) All matter is composed of tiny indivisible
particles called atoms
2) Atoms are indestructible*
(Law of Conservation of Mass)
3) Atoms of an element have identical
chemical and physical properties
4) Atoms of different elements have
different properties
5) Atoms of two or more different elements
can combine in constant ratios to make
new substances
The Atomic Timeline
J. J. Thomson – used a cathode ray tube to prove that atoms were made
up of positive and negative sub-atomic particles (1897)
By manipulating the magnetic field
surrounding the CRT, he found he could
bend the stream of negatively changed
particles.
The particles are named electrons and are
assigned the charge of -1.
Knowing that all substances were
inherently neutral he surmised that there
must be a particle with a charge equal in
magnitude yet opposite in polarity.
The proton, assigned as +1 was
discovered later by Goldstien.
The Atomic Timeline
Thomson s Cathode Ray Tube...

...matter and all life. The history of the study of the atomic nature of matter is the thinking process that goes on in the scientist’s heads. Further progress in the understanding of atoms did not occur until very famous scientist created the atomictheory. Here are some scientists who changed the way we learn about the atom, and the atomic nature of all life.
Ernest Rutherford.
Ernest Rutherford was another scientist that changed the atomic model. Rutherford was studding physics up until his junior years of schooling and since then he had an interest in it. Rutherford was born on the 30 August 1871 in New Zealand. Rutherford was investigating physics everyday he tried lots of experiments.
Rutherford showed that gamma rays were a type of X-ray, and that the alpha and beta rays were tiny particles of matter. Rutherford then showed that the beta particles were electrons.
In 1908 Rutherford demonstrated and made an airtight glass tube with very thin walls, and filled it with the radioactive radium emanation. Alpha particles could penetrate the thin walls of the tube and were collected in a second tube. Rutherford was then inspired to investigate more into Alpha Particles.
Rutherford then began using alpha particles to investigate further into other elements. His theory was if a lot of alpha particles were fired into another substance, it would be then ‘bounced’ off in other...

...Of all of the many scientists who played a major role in the formation of the atomictheory, it is believed that Dalton, Rutherford, Thompson, Bohr, and Planck are the five most influential. The research of this theory has gone on for many years and each and every one of them have brought us closer to our current understanding of the atom today. Each one of them played a special role in the development process of the atom and most importantly, they all reflected on one another. Many influential scientists follow up on one another proving their own theories correct and in time, create challenges for the next scientist to question. This truly, is one of the main reasons we have gotten so far with the atom. These amazing discoveries mostly started taking effect when Dalton came into the picture.
John Dalton (1766-1844), is one of the most influential scientists in the development of the atomictheory. Democritus first suggested the existence of the atom, but it took nearly two millennia before Dalton took the research into his own hands. Dalton's AtomicTheory consists of basic concepts based on the theory that atoms of different elements could be distinguished by differences in their weights. In this he concluded that, 1. All atoms are composed of elements. 2. The atoms of a given element are different from those of any other element. 3. Atoms cannot...

...AtomicTheory-Study Sheet-Updated 9/15
*Reminder-Review Notes and this Question/Answer sheet DAILY to prepare for your next test. Goal: Grade of “A”.
*Flash Review….Test October 7th
How to use this study guide-Print the page and fold between questions and answers OR cover the answer column. Ask yourself the questions and see if you can correctly answer. Use it until you can answer ALL questions quickly with 100% accuracy. Do a little every day, and you will be ready for the next test!
History of AtomicTheory (9/13)
Answers: Questions:
Dalton First scientist to propose a model of the atom
Atom Smallest unit of matter
Element Substance made of multiple identical atoms
Dalton’s incorrect theory The atom is indivisible
Thomson Plum pudding model for the atom
Electrons Particles suggested by Thomson
Rutherford Gold foil experiment
Protons Particles suggested by Rutherford
Nucleus Where Rutherford suggested protons are found
Bohr Theorized that electrons move in set orbits around the nucleus
Chadwick Discovered neutrons
Structure of the Atom (9/14)
Electrons, protons, & neutrons The three sub-atomic particles are…
Proton Sub-atomic particle found in the nucleus; + charge
Electron Sub-atomic particle that orbits the nucleus; - charge
Neutron Sub-atomic...